The present invention relates to a particle control device and a particle control method for use in a vacuum processing apparatus; and, more particularly, the invention relates to a particle control device and a particle control method for a vacuum processing apparatus that is capable of monitoring and controlling the occurrence of particles in a vacuum processing apparatus.
A vacuum processing apparatus, such as a plasma etching apparatus, generates plasma in a vacuum reactor in a state where the vacuum reactor is charged with etching gases. A predetermined semiconductor circuit is formed by causing radicals and ions, that are generated in the plasma, to react with a wafer surface to be etched. In such a plasma etching apparatus, reaction products, which are generated in the etching process, are deposited on the inner walls and electrodes of the vacuum reactor. The deposited reaction products tend to strip off from the inner walls and the electrodes after a certain period of time and to float as particles inside the vacuum reactor.
Further, the plasma etching apparatus is provided with many mechanical components that serve as particle sources, such as a robot for carrying wafers to or from the vacuum reactor and valves provided on wafer transferring passages.
Particles which are produced from such components and float inside the vacuum reactor adhere on the wafer surface during the etching process and the like, or they fall on the wafer surface when the plasma discharge is terminated, after the completion of the etching process. The particles which have adhered or fallen on the wafer surface cause imperfect etching and produce failures in subsequent processes, ultimately leading to a decreased yield or reduced reliability of the semiconductor products.
In a typical semiconductor manufacturing line, apparatus control is conducted in such a manner that a wafer for particle inspection (dummy wafer), or a surface of a product wafer that has been processed, is reviewed periodically by using a particle inspection device to detect the number of particles present on the wafer surface and the particle sizes of the particles. However, this method cannot detect particles during the processing of the product wafer. With the conventional method, therefore, a large number of defective wafers will undesirably be produced until the particles are detected in the next inspection.
Japanese Patent Laid-open No. 2002-57143, for example, discloses a floating particle detector that is capable of real-time detection (in-situ measurement) of particles during the processing of a wafer, which relates to the above-mentioned problem. This device irradiates the inner walls of a vacuum reactor in a semiconductor manufacturing apparatus with laser light, which is emitted from a laser light source, and detects the laser light which is scattered from particles therein, using an optical system for scattered light detection, thereby detecting the particles floating inside the vacuum reactor.
Also, Japanese Patent Laid-open No. 6-201600 discloses a particle measurement system that is capable of measuring particles floating inside a vacuum reactor, in synchronization with the processing of the wafers, one by one, during the processing of one lot of wafers, and of displaying on a display unit or printing out the particle measurement result.
Although the floating particle detector disclosed in Japanese Patent Laid-open No. 2002-57143 is capable of detecting the presence of particles in the semiconductor manufacturing apparatus, it has difficulty in determining the particle sources. Further, according to the system disclosed in Japanese Patent laid-open No. 6-201600, it is possible to detect on which wafer, in the one lot, the particles are present; however, this system also has difficulty in determining the particle sources. That is to say, although it is possible with the conventional techniques to detect the presence of particles and when the particles appear, they have difficulty in determining the particle sources. If the particle sources are not specified, it is difficult to determine what countermeasure to take, and it is impossible to provide a drastic solution to the occurrence of particles in the apparatus.
If particles are present in the apparatus, the vacuum reactor is usually opened to the air and cleaned by using water or an organic solvent. However, since such treatment is typically performed without knowing the cause of the occurrence of the particles, the particles will appear again soon after the cleaning in many cases. Further, since it takes a considerably long period of time to effect cleaning of the vacuum reactor, the operation rate of the vacuum reactor is decreased, resulting in a reduction in the productivity of the manufacturing line.